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Project Trial-wise SBHM Coefficients to Scalar Amplitudes

Source: R/sbhm_project.R
sbhm_project.Rd

Given trial-wise coefficients in the shared basis (rxntrialsxV) and the voxel-specific matched library coordinates alpha_hat (rxV), compute scalar amplitudes per trial and voxel via least-squares projection: a = (alpha' beta) / (alpha' alpha).

Usage

sbhm_project(beta_rt, alpha_hat)

Arguments

beta_rt

3D array of shape r x ntrials x V containing per-trial coefficients in the SBHM basis (as returned by OASIS with K=r, reshaped).

alpha_hat

Numeric matrix rxV of matched library coordinates per voxel (e.g., sbhm_match()$alpha_hat). These should be in the same coordinate system as beta_rt (unwhitened, not L2-normalized) for interpretable amplitudes.

Value

Numeric matrix ntrials x V of scalar amplitudes. Zero-norm or non-finite coordinates are unidentified and fail explicitly. When basis or voxel names are present, both inputs must provide the same complete unique identities; alpha_hat is reordered to beta_rt.

Examples

# \donttest{
  set.seed(1)
  r <- 2; ntrials <- 3; nvox <- 2
  alpha_hat <- matrix(rnorm(r * nvox), r, nvox)
  beta_rt <- array(rnorm(r * ntrials * nvox), c(r, ntrials, nvox))
  amps <- sbhm_project(beta_rt, alpha_hat)
  dim(amps)
#> [1] 3 2
# }